Hyporeninemic hypoaldosteronism in RMND1-related mitochondrial disease

Background: RMND1 is a nuclear gene needed for proper function of mitochondria. A pathogenic gene will cause multiple oxidative phosphorylation defects. A renal phenotype consisting of hyponatremia, hyperkalemia, and acidosis is frequently reported, previously considered to be due to aldosterone insensitivity. Methods: Clinical features and pathophysiology of three patients will be reported. DNA of these patients was subjected to exome screening. Results: In the first family, one pathogenic heterozygous and one highly probable heterozygous mutation were detected. In the second family, a homozygous pathogenic mutation was present. The electrolyte disbalance was not due to aldosterone insensitivity but to low plasma aldosterone concentration, a consequence of low plasma renin activity. This disbalance can be treated. In all three patients, the kidney function declined. In the first family, both children suffered from an unexplained arterial thrombosis with dire consequences. Conclusions: Hyporeninemic hypoaldosteronism is the mechanism causing the electrolyte disbalance reported in patients with RMND1 mutations, and can be treated.